Typically, as power systems for an aircraft, three kinds of systems, which are a hydraulic system, a breed air system, and an electric system, are incorporated into the aircraft. The hydraulic system is employed for the operation of landing gears, control surfaces, etc. The breed air system is employed for the operation of air conditioning devices, pressure application devices, de-icing devices, and others, in the interior of the aircraft. The electric system is employed for the operation of electric devices and electronic devices. In recent years, there has been a trend that at least a portion of the hydraulic system and a portion of the breed air system are replaced by the electric system having a higher efficiency. For example, as actuators (including an actuator for controlling the control surface) mounted to the aircraft, electric (electrically driven) actuators have been widely used, instead of conventional hydraulic (hydraulically powered) actuators. The aircraft in which the hydraulic system, the breed air system, and other system are replaced as much as possible by the electric system, is typically named MEA (more electric aircraft).
It is known that with a progress of the MEA, a change (fluctuation) in a power supply voltage tends to occur, and the electric system tends to be unstable. For example, in the case of the electric actuator, great regenerative power is generated in a driving motor, and thereby a voltage in the electric system rises significantly temporarily (for a certain time). In addition, the electric power is returned to a generator provided in an engine, and thereby an engine gear box might be adversely affected due to back rush. Or, if power loads supplied with the electric power from the electric system, (devices mounted in the aircraft and supplied with electric power from the electric system) increase temporarily, a significant voltage decrease (drop) might be generated.
It is known that in the electric system in which the MEA has progressed, various configurations are employed to address the above stated voltage increase or voltage decrease (drop). For example, it is known that to address regenerative power from the actuator, a resistor is built into a controller of the actuator. In accordance with this configuration, the regenerative power from a driving motor is converted into heat by the resistor and consumed, which prevents the regenerative power from returning to the electric system. It is also known that to address a voltage decrease due to a temporary increase in power loads, an AC power generator having a power generation capacity made greater according to the voltage decrease is employed.
However, in the above stated conventional configurations, a weight of the aircraft might probably increase. For example, in the former configuration, a large-sized resistor is required to adequately consume the great regenerative power. Therefore, the size of the controller of the actuator increases and heat generated increases, which causes a need for a large-sized heat radiator. Because of incorporation of the large-sized controller and the large-sized heat radiator into the aircraft, the weight of the aircraft increases. In the latter configuration, the size of the AC power generator increases due to the increase in the power generation capacity, and therefore, the weight of the aircraft increases. Moreover, in the former configuration, although the heat radiator is provided, unnecessary heat generation occurs. Therefore, it is required that the controller be designed in view of an influence of the heat generation.
Accordingly, for example, Patent Literature 1: US Patent Publication NO. 2009/0302153 discloses an electric system in which surplus electric power such as regenerative power is absorbed or deficient electric power due to a voltage decrease is made up for, by using a DC power supply such as a battery and a capacitor, in a small-sized aircraft.